Multiplier coupling system



P. T. FARNSWORTH 40,285

MULTIPLIER COUPLING SYSTEM Filed March 22, 1937 INVENTOR. P/ulo '7.- Far'nsworlh I BY ,6 22 QW W Patented Dec. 13, 1938 UNITED STATES PATENT OFFICE mmrrruna COUPLING srsrrnvr Philo T.

Farnsworth,

Springfield Township Application -March 22,

14 Claims.

My invention relates to electron multipliers, and more particularly to a means and method of coupling an external circuit to the multiplier in such a manner that variations in load have a minimum effect on the operation of the multiplier.

Among the objects of my invention are: To provide an electron multiplier and coupling therefor; to provide a means and method of abstracting power from an oscillating electron multiplier with a minimum of oscillation disturbance; to provide a means and method of collecting electrons after electron multiplication; to provide a means of coupling a standard frequency oscillator to a power consuming circult; and to provide a simple, eillcient and stable means and method of abstracting power from an electron multiplier.

My invention possesses numerous other objects and features of advantage, some of which, together with the foregoing, will be set forth in the following description of specific apparatus embodying and utilizingmy novel method. It is therefore to be understood that my method is applicable to other apparatus, and that I do not limit myself, in any way, to the apparatus of the present application, as I may adopt various other apparatus embodiments, utilizing the method, within the scope of the appended claims.

Referring to the drawing:

Figure 1 is a longitudinal sectional view through a preferred form of the tube of my invention, together with a diagrammatic circuit for placing the device in operation.

Figure 2 is a cross sectional view, taken as indicated by the line 2-2 in Figure 1.

Figure 3 is an enlarged sectional view of a portion of the device showing an alternative method of coupling the output of a multiplier to a transmission line.

In my prior Patent No. 2,071,516, granted February 23, 1937, entitled Oscillation generator, I have described a cold cathode electron multiplier capable of self-oscillation. One modiiication of this device has been shown to be a diode, and in my application, Serial No. 132,327, filed March 22, 1937, entitled Diode oscillator tube construction, I have described several forms which this diode may take, a preferred form being merely a cathode cylinder enclosing an apertured anode, the cylinder having its inner surface sensitized for the generation of secondary electrons at a ratio greater than unity upon electron impact therewith.

1937, Serial No. 132330 By connecting an external resonant circuit between anode and cathode, and by supplying the anode with a source of potential more positive than the cathode, I have been able to cause the device to self-oscillate by causing the oscillation within the cathode chamber of an electron cloud which repeatedly impacts the cathode to generate secondaries. The device will reach an equilibrium value, maintain itself in self-oscillation, and power can be drawn therefrom.

a In common with other generators, this oscillator is also sensitive to variations in load, and it is desirable, therefore, when the device is being used as a master oscillator or standard frequency oscillator feeding a power consuming circuit which may vary in its demand, to take precautions that the power absorbed shall not interfere with the operation of the oscillator.

The present invention deals with a means and method of abstracting power from an electron multiplier, preferably a diode, in such a manner that it will not, to any great extent, interfere with the operation of the multiplier itself.

Broadly as to method, my invention comprises oscillating a cloud of electrons against and away from a cathode capable of generating secondary electrons at a ratio greater than unity upon each impact therewith, collecting a portion of the electrons, segregating another portion of the electrons and directing them away from the oscillating structure, and thereafter collecting them within a unipotential space.

Broadly, as to apparatus, my invention comprises a cathode capable of emitting secondaries at a ratio greater than unity upon electron impact therewith, and an anode so positioned and energized as to cause an oscillation of an electron cloud against and away from the cathode.

Self-oscillation is preferably obtained by connecting the anode and cathode with a resonant circuit and energizing the anode to a potential more positive than the cathode, or, putting it another way, in this particular case making the cathode more negative than the anode, as I prefer to work with the anode at ground potential. A portion of the oscillating cloud is collected by the anode; another portion passes through an aperture in the cathode into the interior of a Faraday cylinder, and is there collected. The Faraday cylinder is maintained at a potential higher than either the anode or cathode of the multiplier, and in my preferred form is connected by a resonant circuit to the cathode.

The advantages of such a means and method may be more fully understood by direct reference to the drawing, which shows two preferred structural embodiments of my invention utilizing my improved method.

In Figure 1, an envelope I, which may be a cylinder, is normally closed at one end and has the other end closed by a reentrant stem 2. Carried on the stem 2 by appropriate supports is a cylindrical cathode l and an apertured anode 6, .which in this case may be formed by winding a fine refractory wire 6 on upright supports I. I also prefer to have the two electrodes concentrically positioned with respect to each other.

At one point in the surface of the cathode I cut a cathode aperture, and partially close it with a screen 9. While the size and shape of this aperture is not important, I prefer to utilize an aperture shaped to match the open end of a tubular collecting electrode ill, the open end being positioned closely adjacent the screen 6 and extending away from the cathode on the outside thereof. I also prefer to position the aperture midway between the open ends of the cathode, as it is here that the maximum cone} centration of electrons usually occurs. Tubular electrode 10 is positioned in a side arm ll of the envelope, and is supported by a lead I2 enter-"a ing the end of the side arm.

In order to operate the device, I prefer to connect a multiplier resonant circuit l4 between anode 6 and ground. A radio frequency ground is provided for cathode 4 by the connection of by-pass condenser l5 between cathode 4 and ground. Collecting cylinder I0 is raised to a relatively high positive potential by collecting source I6 in series with a collector resonant circuit il. Energizing the device as shown, it will be found that the anode 6 is held at a D. 0. ground potential, but is connected to the cathode through the resonant circuit l4 and by-pass condenser l6. Cathode 6 is maintained at a fixed negative D. 0. potential but with a ground R. F. potential. Thus there will be very little coupling between collecting cylinder Ill and anode 6. Under these conditions the diode combination of cathode l and anode 6 becomes a self-oscillator.

I prefer to sensitize theinner surface of cathode I so that secondary electrons will be emitted on electron impact therewith at a 1 to 1 ratio when electrons impact at about twenty volts velocity, and if I form the cathode I of silver, oxidize its surface, and sensitize the surface with caesium, I find that secondaries can be produced with ratios as large as 10 or 12 to 1 at higher velocities.

Due to the action of the resonant circuit I4, and the fact that anode 6 is at a potential more positive than cathode 4, continuous oscillation of the diode structure takes place as described in my prior applications referred to above, with the electrons repeatedly and cyclically impacting cathode l and producing secondaries, some of which are constantly being collected by anode I and being used to maintain self-oscillation. However, in the vicinity of the aperture screen 6 some of the electrons approaching the surface of the cathode at this point will, of course, pass through the screen and enter the space enclosed by collecting cylinder Ill, and eventually be collected.

I prefer to utilize a tubular collector for several reasons. First, electrons of all velocities will be collected substantially simultaneously, the higher velocityelectrons passing through to the the cathode.

suming circuit.

end of the cylinder and the lower electrons being collected by the side walls without going to the end. Furthermore, the cylinder has a distinct focusing action, and as most of the electrons passing through the screen 9 will be of high velocity, they will liberate heat at the area of collection. Inasmuch as the sensitive caesium surface which I prefer to use is readily affected adversely by heat, it is of great advantage to have the hot spot where the majority of'electrons are collected, as faraway as possible from The tubular electrode is an eihcient means of collecting all the electrons passing through the screen 9, and at the same time keeps the impact area heated by the high velocity electrons at a distance away from the sensitized cathode surface.

As an example of the efliciency of the device, coupled in this manner to an external circuit such as H, I have found that when 600 volts difference is utilized between the multiplier anode and cathode, and 2000 volts between multiplier anode and collector III, that anode 6 will, in one embodiment, pick up ten milliamperes of current, whereas the collector willv pick up two milliamperes of current. This amount ofpower may beliabstracted with the oscillator with a minimum of disturbance of the amplitude or frequency of the oscillator, and therefore the variations in circuit II have little or no effect on the oscillator -itself. I

It is obvious that circuit I! may be the power consuming circuit in the device shown in Figure 1. In Figure 3 I have shown a coupling means whereby the power collected by cylinder l0 may be transferred directly into a tubular conductor for use-as desired. Here, the lead I! for the tubular electrode in passes, preferably, through the side wall of the envelope I, leaving the end wall of the side arm ll clear. Under these conditions a tubular conductor 2| may be slipped on over the side arm outside of the envelope wall, and is capacitatively coupled to the collector i0. In this case collector I0 is fed from source l6 through R. F. choke 22.

The devices I have shown here illustrate, of course, only two particular forms of power con- Other structures and other circuits embodying my invention will be apparent to those skilled in the art, and are deemed to fall within the scope of my invention as defined within the appended claims. a

The invention, while described as applied to a multiplier diode, is obviously applicable to any electrode where electrons repeatedly and cyclically impact the surface thereof with a velocity sumcient to pass through an aperture therein.

I claim:

1. In combination, an electron multiplier comprising an envelope containing aunipotential cathode capable of emitting secondary electrons at a ratio greater than unity upon electron impact therewith, and having an aperture therein, an anode on one side of said cathode, external circuit means for causing electrons to make continuous cyclical impacts with said cathode at a velocity sufficient to produce secondaries and sustain oscillation of said electrons, and a hollow collector on the other side of said cathode having an open end adjacent said aperture to receive electrons passing therethrough.

2. In combination, an electron multiplier comprising an envelope containing a unipotential cathode capable of emitting secondary electrons at a ratio greater than unity upon electron im- 1| pact therewith, and having an aperture therein, an anode on one side of said cathode, external circuit means for causing electrons to make continuous cyclical impacts with said cathode at a velocity suflicient to produce secondaries and sustain oscillation of said electrons, and an elongated tubular electrode extending away from said cathode and having an open end adjacent said aperture to receive electrons passing therethrough.

3. In combination, an electron multiplier comprising an envelope containinga unipotential cathode capable of emitting secondary electrons at a ratio greaterthan unity upon electron impact therewith, and having an aperture therein, an anode on one side of said cathode, external circuit means for causing electrons to make continuous cyclical impacts with said cathode at a velocity sumcient to produce secondaries and sustain oscillation of said electrons, an elongated tubular electrode extending away from said cathode and having an open end'adjacent said aperture to receive electrons passing therethrough, and an external circuit connected from said cathode to said tubular electrode including a source of positive potential for said electrode.

4. In combination, an electron multiplier comprising an envelope containing a unipotential cathode capable of emitting secondary electrons at a ratio greater than unity upon electron impact therewith, and having an aperture therein, an anode on one side of said cathode, external circuit means for causing electrons to make continuous cyclical impacts with said cathode at a velocity suilicient to produce secondaries and sustain oscillation of said electrons, an elongated tubular electrode extending away from said cathode and having an open end adjacent said aper ture to receive electrons passing therethrough, an external circuit connected from said cathode to said tubular electrode including a source of positive potential for said electrode, and a circuit resonant to the oscillation frequency, connecting said tubular electrode to said cathode.

5. In combination, an electron multiplier comprising an envelope containing a unipotential cathode capable of emitting secondary electrons at a ratio greater than unity upon electron impact therewith, and having an aperture therein, an anode on one side of said cathode, external circuit means for causing electrons to make continuous cyclical impacts with said cathode at a velocity suiiicient to produce secondaries and sustain oscillation of said electrons, an elongated tubular electrode extending away from said cathode and having an open end adjacent said aperture to receive electrons passing therethrough, an external circuit connected from said cathode to said tubular electrode including a source of positive potential for said electrode, a circuit resonant to the oscillation frequency connecting said tubular electrode to said cathode, and a tubular conductor surrounding said tubular electrode outside of said envelope.

6. In combination, an electron multiplier comprising an envelope containing a unipotential cathode capable of emitting secondary electrons at a ratio greater than unity upon electron impact therewith, and having a screened aperture therein, an anode on one side of said cathode, external circuit means for causing electrons to make continuous cyclical impacts with said cathode at a velocity sumcient to produce secondaries and sustain oscillation of said electrons, and a make continuous cyclical impacts with said cath-- ode at a velocity sufilcient to produce secondaries and sustain oscillation of said electrons, and an elongated tubular electrode extending away from said cathode and having an openfend adjacent said aperture to receive electrons passing therethrough. a

8. In combination,.an electron multiplier comprising an envelope containing a unipotential cathode capable of emitting secondary electrons at a ratio greater than unity upon electron im pact therewith, and having a screened aperture therein, an anode on one side of said cathode, ex ternal circuit means for causing electrons to make continuous cyclical impacts with said cathode at a velocity suflicie'nt to produce secondaries and sustain oscillation of said electrons, an elongated tubular electrode extending away from said cathode and having an open end adjacent said aperture to receive electrons passing therethrough, and an external circuit connected from said cathode to said tubular electrode including a source of positive potential for said electrode.

9. In'combination, an electron multiplier comprising an envelope containing a unipotential cathode capable of emitting secondary electrons at a ratio greater than unity upon electron impact therewith, and having a screened aperture therein, an anode on one side of said cathode, external circuit means ior causing electrons to make continuous cyclical impacts with said cathode at a velocity sufficient to produce secondaries and sustain oscillation of said electrons, an elongated tubular electrode extending away from said cathode and having an open end adjacent said aperture to receive electrons passing therethrough, an external circuit connected from.

said cathode to said tubular electrode including a source of positive potential for said electrode, and a circuit resonant to the oscillation frequency, connecting said tubular electrode to said cathode.

10. In combination, an electron multiplier comprising an'envelope containing a unipotential cathode capable of emitting secondary electrons at a ratio greater than unity upon electron impact therewith, and having a screened aperture therein, an anode on one side of said cathode, external circuit means for causing electrons to make continuous cyclical impacts with said cathode at a velocity sufficient to produce secondaries and sustain oscillation of said electrons, an elongated tubular electrode extending away from said cathode and having an open end adjacent said aperture to receive electrons passing therethrough, an external circuit connected from said cathode to said tubular electrode including a source of positive potential for said electrode, a circuit resonant to the oscillation frequency connecting said tubular electrode to said cathode, and a tubular conductor surrounding said tubular electrode outside of said envelope.

11. The method of abstracting power from an electron multiplier, which comprises oscillating a cloud of electrons against and away from a surface to produce secondary emission at a ratio hollow collector on the other side of said cathode greater than unity at each impact therewith,

collecting a portion of said electrons, utilizing the energy of the collected portion to maintain oscillation of said cloud, directing another portion of said electrons away from said surface, and collecting said latter electrons in a unipotential space.

12. The method of abstracting power i'rom'an electron multiplier, which comprises oscillating a cloud of electrons against and away from a surface to produce secondary emission at a ratio greater than unity at each impact therewitnvcollecting a portion of said electrons, utilizing the energy of the collected portion to maintain oscillation of said cloud, directing another portion of said electrons away from said surface, and electrostatically focusing said latter electrons on a spot removed from said surface.

13. The method 01 abstracting power from an electron multiplier, which comprises oscillating a cloud of electrons against and away from a surface to produce secondary emission at a ratio greater than unity at each impact therewith, col.- lecting a portion of said electrons, utilizing the energy of the collected portion to maintain oscillation of said cloud, directing another portion of said electrons away from said surface, and collecting all velocity components of said latter electrons at substantially the same time.

14. The method of abstracting power from an electron multiplier, which comprises oscillating a cloudoi electrons against and away from a surface to produce secondary emission at a ratio greater than unity at each impact therewith, 001- lecting a portion of said electrons, utilizing the energy of the collected portion to maintain oscillation of said cloud, directing another portion of said electrons away from said surface, collecting all velocity components of said latter electrons at substantially the same time, and utilizing the energy of said latter electrons in a work circuit.

Piano '1'. FARNSWORTH. 

